This invention relates to an apparatus for treating workpieces and particularly, to a device and method for coating internal cavities of workpieces such as fastener nuts with fluid materials.
Various coatings of fluid materials are applied to the internal surfaces of nut type fastener parts as well as external surfaces of the corresponding fastener parts. Such coatings may be used as sealants to prevent fluid leakage through the fastened connection and/or as a means of providing adhesive bonding between parts, thereby increasing unfastening effort.
Although various machines are known to the prior art for coating workpieces with fluid materials, it is desirable to provide an improved machine which features increased production rate capability and reliability. It is further desirable to provide such a device which prevents the fluid coating material from being discharged by the machine when a workpiece is not placed at a workstation, thereby avoiding waste of the material and preventing it from contaminating the working mechanism of the machine. It is also advantageous to provide such a machine which accurately applies the fluid coating material at the desired location within the internal workpiece cavity. It is further advantageous to provide such a device for which the rate of production may be varied in accordance with production plant schedules. Finally, it is desirable to provide a workpiece treating machine which may be conveniently and easily modified and/or adjusted to accept different types of workpieces and workpieces of differing dimensions.
The above benefits are provided by a machine and method according to this invention. The device described herein includes a plurality of workstations which are attached to a rotating turntable assembly. Each workstation includes an elongated cylinder having internally disposed first and second plungers. The first plunger features a cam follower which moves along a cam surface as the turntable is rotated, causing the plunger to be displaced between two positions. An elongated hollow probe is attached to the first plunger and is caused to move between a position enclosed within the cylinder to a position extended into the workpiece as the turntable is rotated. A valve stem protrudes from the probe which causes the fluid coating material to be applied to the internal cavity of the workpiece when it becomes depressed against a stop. In accordance with a significant aspect of this invention, a second plunger is also provided within the cylinder which performs the dual functions of acting to clamp the workpiece as the probe is inserted therein and also acting to prevent the flow of coating material from the exit ports of the probe when a workpiece is not placed at the workstation; which might occur for instance, when the workpiece flow from a feeder mechanism is interrupted. Since this device includes a continuously rotating turntable, its drive system is less complex than machines which require that workpieces be moved between and stopped at indexed positions.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.